Q&A for How to Measure Surface Tension

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  • Question
    Can I use pennies instead of water droplets or pins?
    Community Answer
    No. Pennies have a very dense and heavy surface rather than water droplets or pins.
  • Question
    I have a homemade, non-bulb pipette, 66 cm long. When shut, fluid does not escape. Is there a universal formula for this effect? Surface tension, adhesion, gravity, air pressure?
    Community Answer
    If the fluid in the pipette's exit flowed out, it would create a near vacuum, sucking the liquid back in. No gas can replace the liquid, so the only gas available attempts to fill the space. This creates the sucking force (like the principle of the vacuum cleaner) that keeps the liquid in place.
  • Question
    What do I do if method 2 is not working? I'm submerging the tube in water, but there is no liquid above where the liquid in the dish ends.
    Community Answer
    Use a capillary tube that has a small inner radius. Moreover, use a travelling microscope for better readings and therefore better results.
  • Question
    What does N/m and N/g mean?
    Community Answer
    These mean Newtons per meter and Newtons per gram, respectively.
  • Question
    The capillary action is not working and I have tried using a smaller straw. Any advice?
    James Windsor
    Community Answer
    A smaller straw will be easier. The experiment was also using the incorrect number for density of water which should be 1000kg/m3 not 1kg, so in the example given water would only rise 0.5mm not 50cm.
  • Question
    Is the contact angle forgotten in the formula of the capillary action?
    James Windsor
    Community Answer
    This is a valid point - the contact angle needs to be 90 degrees to the surface of the water.
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